Jupiter
was once considered a possible haven for life. Although
the planet is gaseous in nature, it was thought that the swirling
clouds of gas that appeared to contain significant traces of water
vapor, ammonia, methane and other compounds, would be ideal conditions
for life to evolve. The upper cloud layers were thought
to be warm enough, cool enough, calm enough, and have an ample
supply of lightning to supply the energy necessary to provide
the "spark of life".

Expectations
remained high until the Galileo
Spacecraft launched a probe into Jupiter's cloud tops.
The results were spectacular in terms of the data collected, but
a disappointment to life-scientists. Jupiter's clouds were
found to be almost devoid of organic precursors and the quantity
of water vapor was found to be ten times lower than predicted.
In the upper atmosphere the temperature was several hundred degrees
higher than expected, at around 700 C (1300 F), and wind speeds
reached 520 kph (330 mph), 160 km (100 miles) below the cloud
tops. While the wind is potentially useful in remixing molecules
and so allowing organic elementary chemistry to occur, it is so
severe that it is likely to destroy the structure of any potential
living entity that might be forming. It had been thought
that the atmospheric flow at this altitude would have been almost
zero. In addition, although thunderstorms
were detected, the expected electrical activity in the clouds
that could promote chemical processing was found to be almost
non-existent.

So,
conditions were found to be non-conducive for life at the upper
levels. Below this the temperature and pressure rises rapidly
and no form of life as we know it would be able to survive at
lower depths in the gas giant.

In
common with other gas giants with no discernible solid surface,
any life-bearing space debris swallowed up by the planet would
be crushed and heated out of existence, as it plunged below the
clouds. Any life within the debris, whether in ice or rock,
would be destroyed.